Pope Francis installed in Mass at the Vatican

Pope Francis urged princes, presidents, sheiks and thousands of ordinary people gathered for his installation Mass on Tuesday to protect the environment, the weakest and the poorest, mapping out a clear focus of his priorities as leader of the world's 1.2 billion Catholics. The Vatican said 150,000 to 200,000 people attended the Mass, held under bright blue skies after days of chilly rain and featuring flag-waving fans from around the world. In Buenos Aires, thousands of people packed the central Plaza di Mayo square to watch the celebration on giant TV screens and erupted in joy when Francis called them from Rome, his words broadcast to the crowd over loudspeakers.